1. Field of the Invention
The present invention relates to an ultrasonic cleaner for irradiating an object to be cleaned in a cleaning liquid with ultrasonic waves generated from an ultrasonic transducer and to a wet treatment nozzle comprising the same.
2. Related Art
Heretofore, an ultrasonic shower cleaner 450 as shown in FIG. 21 has been used to clean liquid crystal panels and semiconductor wafers. In this ultrasonic shower cleaner 450, a hollow portion 452 for storing a cleaning liquid S is formed in the inside of a housing 451 and a liquid feed port 453 for supplying the cleaning liquid S into the hollow portion 452 is formed in an upper portion of a side wall of the housing 451 as shown in the figure. A nozzle 454 for discharging the cleaning liquid S is formed in the lower portion of the housing 451 and an ultrasonic transducer 455 is installed on the top surface of the housing 451. To clean an object P to be cleaned, this object P is caused to pass under the ultrasonic shower cleaner 450 and the cleaning liquid S is poured upon the surface of the object P by driving the ultrasonic transducer 455 by means of an unshown ultrasonic wave generator.
However, as the amount of the cleaning liquid is large in this cleaning method, a water-saving ultrasonic cleaner 460 shown in FIG. 22 is conceivable. This ultrasonic cleaner 460 has a housing 461 whose center portion 461a is depressed and whose end portion 461b is formed like a visor, an ultrasonic transducer 462 is placed on the surface of the center portion of the housing 461, and the object P passing through the cleaning liquid S under the housing 461 is irradiated with ultrasonic waves to be cleaned by vibrating the ultrasonic transducer 462.
An ultrasonic cleaner 470 shown in FIG. 23 is also conceivable though its cleaning method is similar to the above cleaning method. This ultrasonic cleaner 470 has a first housing 471 whose center portion 471a is depressed and whose end portion 471b around the center portion 471a is formed like a visor and a second housing 472 surrounding this first housing 471, whose center portion 472a is depressed and whose end portion 472b around the center portion 472a is formed like a visor. A packing 473 is sandwiched between the end portions 471b and 472b of these housings 471 and 472, and a hollow portion 474 is formed between the first housing 471 and the second housing 472. Further, a liquid for preventing empty heating, such as water 475, is filled in this hollow portion 474 and an ultrasonic transducer 476 is installed on the surface of the center portion of the first housing 471 so that the object P passing through the cleaning liquid S under the second housing 472 is irradiated with ultrasonic waves through water 475 in the hollow portion 474 to be cleaned by vibrating the ultrasonic transducer 476.
In the case of the ultrasonic cleaner 460 shown in FIG. 22 which is of a water-saving type, the vibration energy of the ultrasonic transducer 462 vibrates the bottom surface of the housing 461 and is radiated onto the object P through the cleaning liquid S. However, it also vibrates the wall surface of the housing 461, resulting in the waste of energy.
In the case of the ultrasonic cleaner 470 shown in FIG. 23, the thickness of the packing slightly differs according to clamping force, whereby the thickness of the hollow portion 474, that is, the depth of water filled in the hollow portion 474 differs. In this system that the object is irradiated with ultrasonic waves through water, sound pressure radiated from the sound wave radiation surface which is the bottom surface of the center portion of the second housing greatly changes according to variations in the depth of water from the relationship between the wavelength of an ultrasonic wave and the depth of water. In other words, the radiation sound pressure is greatly affected by the clamping force of the packing and lacks stability. When the depth of water is not appropriate and radiation sound pressure from the ultrasonic wave radiation surface is small, part of energy radiated from the ultrasonic transducer which is not used effectively may be used and wasted as energy for vibrating the wall surface of the second housing and may affect other devices by the vibration of the housing.
It is an object of the present invention to provide an ultrasonic cleaner which facilitates the control of ultrasonic wave radiation efficiency and a wet treatment nozzle comprising the same.
According to a first aspect of the present invention, there is provided an ultrasonic cleaner which comprises a housing having an U-shaped cross section, an ultrasonic transducer placed on the inner surface of the U-shaped portion of the housing and a weight provided on the housing to prevent the vibration of the wall of the housing.
According to this constitution, ultrasonic energy is radiated efficiency from the bottom as ultrasonic waves without leaking to the wall.
The above weight may be placed on the inner wall surface or outer wall surface if it improves the rigidity of the housing. It may be placed on at least one of the outer wall surface and inner wall surface of the housing.
The above weight prevents energy from the ultrasonic transducer from escaping to the housing. If it is placed on the inner bottom surface where the ultrasonic transducer is installed, ultrasonic energy does not leak to the outside from the weight installation portion. Therefore, it may be placed on the inner bottom surface of the housing in an area where vibration caused by the ultrasonic transducer is not prevented.
The above weight may be formed by changing the thickness of the housing itself as means of improving the rigidity of the housing because the same function can be achieved by making the thickness of a predetermined portion larger than other portions.
Preferably, the above weight is provided on the entire surface of the wall of the housing to improve the rigidity of the housing and prevent energy from the ultrasonic transducer from propagating to the wall by shifting the characteristic frequency of the wall from the frequency of vibration input to prevent the resonance of the wall.
According to a second aspect of the present invention, there is provided a wet treatment nozzle which comprises an introduction passage for introducing a treatment liquid on one side, an exhaust passage for exhausting the treatment liquid after a wet treatment on the other side, and a vibration guide member for guiding the treatment liquid introduced from the introduction passage to an object to be treated and wet treating the object while vibrating it, wherein the vibration guide member is the above-mentioned ultrasonic cleaner.
With this nozzle, the treatment liquid can be supplied onto the surface to be treated and the used treatment liquid can be suitably exhausted through the exhaust passage, thereby making it possible to always treat the surface with a fresh treatment liquid and prevent the surface from being contaminated by the used treatment liquid again.
Since the treatment liquid is held in a space between the surface to be treated and the vibration guide member with pressure balance such as interfacial tension, the surface can be wet treated with the required minimum of the treatment liquid and ultrasonic vibration can be provided to the surface to be treated without fail.
Since the ultrasonic cleaner having the weight is used as the vibration guide member, ultrasonic energy required for a wet treatment is obtained and an extremely good treatment can be made with the required minimum of the treatment liquid.
This wet treatment nozzle is provided with pressure control means of controlling a difference between the pressure of the treatment liquid in contact with the object to be treated and atmospheric pressure to prevent the treatment liquid in contact with the object to be treated from flowing into a passage other than the exhaust passage after a wet treatment. This pressure control means comprises a suction pump provided on a downstream side of the exhaust passage, a liquid feed pump provided on an upstream side of the introduction passage, a pressure sensor for detecting the pressure of the treatment liquid in contact with the object to be treated and a controller for controlling the driving of the suction pump and the liquid feed pump according to a signal from the pressure sensor.
According to a third aspect of the present invention, there is provided an ultrasonic cleaner which comprises a housing having an U-shaped cross section and a hollow portion therein, an ultrasonic transducer placed on the inner bottom surface of the inner U-shaped portion of the housing, a liquid for preventing empty heating charged into the hollow portion to transmit vibration from the ultrasonic transducer to the outer bottom surface of the outer U-shaped portion of the housing, and a weight provided on the housing to prevent the vibration of the wall of the housing.
According to this constitution, vibration is prevented by the weight when the thickness of the hollow portion, that is, the depth of the liquid for preventing empty heating, for example, water does not match the wavelength of an ultrasonic wave according to the fastening degree of a packing and when energy generated by the ultrasonic transducer tries to vibrate the bottom surface of the outer U-shaped portion of the housing through the liquid for preventing empty heating. Therefore, vibration energy returns toward the bottom of the center portion of the housing through the liquid for preventing empty heating and is radiated from the bottom efficiently as ultrasonic waves.
The liquid for preventing empty heating is preferably a degassed liquid. By degassing, the flow rate of the liquid for preventing empty heating (circulation for cooling) can be greatly reduced. If the liquid for preventing empty heating contains many bubbles, the same phenomenon as empty heating may occur.
Since the weight is means of improving the rigidity of the housing itself, it may be placed on the outer wall surface or the inner wall surface. It is desirably placed on at least one of the outer wall surface and the inner wall surface forming the above outer U-shaped portion of the housing.
In this case, the weight may be placed on at least one of the outer wall surface and the inner wall surface forming the inner U-shaped portion of the housing to prevent ultrasonic vibration energy from the ultrasonic transducer installed on the inner U-shaped portion from escaping to the wall by increasing the rigidity of the wall of the inner U-shaped portion.
The weight is placed outside an area corresponding to the ultrasonic transducer installed on the inner U-shaped portion on the inner bottom surface of the outer U-shaped portion to prevent ultrasonic energy from leaking to the wall from a portion around the inner bottom surface of the outer U-shaped portion. The weight is placed outside the ultrasonic transducer installed on the inner U-shaped portion to prevent ultrasonic energy from leaking to the wall from the inner bottom surface of the inner U-shaped portion. Therefore, the weight may be placed on at least one of the inner bottom surface of the outer U-shaped portion and the bottom surface of the inner U-shaped portion of the housing in an area where vibration caused by the ultrasonic transducer is not prevented.
The weight changes the rigidity of the housing itself. As mean of attaining this, a new weight may be added or the thickness of a required portion is made appropriate. Therefore, the means may be formed by changing the thickness of the outer U-shaped portion or the inner U-shaped portion of the housing.
Preferably, the weight is provided on the entire surface of the wall of the housing to improve the rigidity of the housing and prevent energy from the ultrasonic transducer from propagating to the wall by shifting the characteristic frequency of the wall from the frequency of vibration input to prevent the resonance of the wall.
Preferably, the housing is constructed such that a second housing whose center portion is depressed and whose end portion around the center portion is formed like a visor is arranged around a first housing whose center portion is depressed and whose end portion around the center portion is formed like a visor, and a hollow portion is formed between the first housing and the second housing by sandwiching a packing between the end portions of the housings.
In the housing, an appropriate liquid is placed in this hollow portion, thereby making it possible to prevent the breakage of the ultrasonic transducer caused by heating without a wet treatment liquid under the housing. When the wet treatment liquid is located below the housing, sufficient ultrasonic energy can be propagated to the wet treatment liquid.
According to a fourth aspect of the present invention, there is provided an ultrasonic cleaner in which the packing is made of an elastic member having a through hole in the center, the first housing and the second housing are made of a plate member, the elastic member is sandwiched between the visor-like end portion of the first housing and the visor-like end portion of the second housing with a bolt penetrating the end portions, and the thickness of the packing can be changed by adjusting the fastening degree of the bolt.
According to this constitution, the thickness of the elastic member sandwiched between the visor-like end portion of the first housing and the visor-like end portion of the second housing can be adjusted by controlling the fastening degree of the bolt, thereby making it easy to adjust the radiation strength of ultrasonic waves.
According to a fifth aspect of the present invention, there is provided a wet treatment nozzle which comprises an introduction passage for introducing a treatment liquid on one side, an exhaust passage for exhausting the treatment liquid after a wet treatment on the other side and a vibration guide member, interposed between the introduction passage and the exhaust passage, for guiding the treatment liquid introduced from the introduction passage to an object to be treated and wet treating the object while vibrating it, wherein the above vibration guide member is the above-mentioned ultrasonic cleaner of the present invention.
With this nozzle, the treatment liquid can be supplied onto the surface to be treated and the used treatment liquid can be suitably exhausted through the exhaust passage, thereby making it possible to always treat the surface with a fresh treatment liquid and prevent the surface from being contaminated by the used treatment liquid again.
Since the treatment liquid is held in a space between the surface to be treated and the vibration guide member with pressure balance such as interfacial tension, the surface can be wet treated with the required minimum of the treatment liquid and ultrasonic vibration can be applied to the surface to be treated without fail.
In addition, even if the treatment liquid in the space between the ultrasonic vibration guide member and the treatment surface runs short, a liquid for preventing empty heating is existent in the space between the ultrasonic transducer and the ultrasonic vibration guide member, thereby making it possible to prevent the empty heating of the ultrasonic transducer without fail.
This wet treatment nozzle is also provided with pressure control means of controlling the difference between the pressure of the treatment liquid in contact with the object to be treated and atmospheric pressure to prevent the treatment liquid in contact with the object from flowing to the outside of the exhaust passage after the wet treatment.